Science Education Home Home Teachers Students Games Videos VA SOL Programs

Here's a Question!

Circle vs. Triangle

A card with a small triangular hole in it is attached to one end of a meter stick and a piece of paper is attached to the other. The meter stick is pointed towards the sun so that its light passes through the triangular hole and falls on the paper. What shape does the light make on the paper?

Announcer: Frostbite Theater presents... Cold Cuts! No baloney!

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joana: Here's a question for you...

A card with a small triangular hole in it is attached to one end of a meter stick and a piece of paper is attached to the other.

Steve: The meter stick is pointed towards the sun so that its light passes through the triangular hole and falls on the paper.

Joana: What shape does the light make on the paper?

Steve: Does it make a circle?

Joana: Does it make a triangle?

Steve: Does it make a square?

Joana: Or, does it make pentagon?

Pause the video now if you'd like to think it over before we show you what happens.

Up close, it's easy to tell that the triangle is a triangle. But, the further away it is, it's harder to tell what shape it is.

Steve: This triangle is small enough that, from a meter away, its 'triangle-ness' is hard to detect. It basically acts like a pinhole and projects an image of the round sun onto the paper.

Joana: Thanks for watching. I hope you'll join us again soon for another question!

Citation and linking information

For questions about this page, please contact Carol McKisson.